A systematic review on the application of UAV-based thermal remote sensing for assessing and monitoring crop water status in crop farming systems

The accurate assessment and monitoring of crop water status is a critical component of precision agriculture. Over the recent decade, unmanned aerial vehicles (UAVs) integrated with high-resolution thermal technologies, have pioneered a new era in remote sensing, enabling the acquisition of near-real-time data essential for the efficient management of water resources within crop farming systems. With the application of UAV-based thermal sensors, a diverse array of key biophysical and biochemical indicators that serve as critical proxies for crop water status have been evaluated. Therefore, this study adopted a systematic approach to review the progress, challenges, and opportunities in utilizing UAV thermal remote sensing to assess and map the water status within crop farming systems. In particular, this study sought to explore the current state of the literature and identify existing research gaps by analysing bibliometric data and recent trends in the literature. Based on the findings of this study, it was observed that even though UAV thermal remote sensings hold great potential, there currently exists significant research gaps in their application for assessing and monitoring crop water status, particularly in the global south. Furthermore, the results of this study concluded that the majority of the reviewed literature focused on assessing canopy temperature, potentially resulting in the application of UAV thermal sensors in characterizing other crop water-related indicators remaining relatively underexplored in scientific research. Overall, the findings of the review highlight UAV thermal remote sensing as an innovative tool capable of providing high-resolution, robust, and near-real-time datasets for crop water status assessments, therefore, revolutionizing agricultural farming practices.Therefore, this study serves as a stepping stone towards integrating UAV thermal technologies into agricultural practices and achieving robust and spatially explicit information on crop water status for the improved management of farming landscapes.